Hi large shaped bump over the knee leaving a hole ir scarring after healing can be pyoderms gangrenosum.it is a kind of vasculitis
where u get a pyoderma
and leave a papery scar after healing. Do routine investigationss like cbp.cue.esr ct bt and platelet count
.it can be cured by atarax
25 mg at night.broad spectrum antibiotic and application of t-bact ointment along with short course of steriods helps.